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Fundamental sensor feedback limitations for improving rotor angle stability using local frequency or phase angle measurement are derived. Using a two-machine power system model, it is shown that improved damping of inter-area oscillations must come at the cost of reduced transient stability margins, regardless of the control design method. The control limitations stem from that the excitation of an inter-area mode by external disturbances cannot be estimated with certainty using local frequency information. The results are validated on a modified Kundur four-machine two-area test system where the active power is modulated on an embedded high-voltage dc link. Damping control using local phase angle measurements, unavoidably leads to an increased rotor angle deviation following certain load disturbances. For a highly stressed system, it is shown that this may lead to transient instability. The limitations derived in the paper may motivate the need for wide-area measurements in power oscillation damping control. [ABSTRACT FROM AUTHOR]

Modern active distribution networks (ADNs) have become more resilient to service interruptions due to the flexibility offered by integrated distributed energy resources (DERs). Compared to network-owned DERs, directly controlled by the distribution system operator (DSO), a vast majority of DERs controlled by independent virtual power plants (VPPs) are much more difficult to coordinate. The coordination with the VPPs and the management of uncertainty are the two major obstacles in the utilization of these DERs in the ADN restoration (ADNR). This article proposes a hierarchical framework for the sequential ADNR to overcome these two obstacles. The proposed framework adaptively integrates the sequential ADNR planning and the VPP scheduling models based on a comprehensive DSO and VPP coordination scheme to quantify and include the flexibility of VPPs in the ADNR. Furthermore, to address the uncertainty of renewable DERs and loads, a chance-constraint (CC) approach is used in these models. As the probability distributions of the uncertain parameters are not fully known, a distributionally robust reformulation for CCs is proposed that ensures that the solution is robust to any uncertainty distribution defined within a moment-based ambiguity set. The DR reformulation is further linearized to achieve DRCC mixed-integer linear-programming models for ADNR planning and VPP scheduling. Finally, its effectiveness is evaluated on the IEEE 123 node ADN. [ABSTRACT FROM AUTHOR]

An FR4-based full Ka-band 1:4 passive power divider using substrate integrated suspended line (SISL) technology is presented in this letter and it achieves a relatively low insertion loss. A SISL to air-filled substrate integrated waveguide (SIW) T-junction with an iris structure is proposed as the first stage of the divider to obtain wideband matching, and a bandwidth of 61.7% is achieved. The power-handling capability of the power divider is studied. A back-to-back 1:4 power divider was fabricated, and the measured results agree well with the simulated ones. From 25.2 to 40 GHz, i.e., a 45.5% fractional bandwidth, the measured return loss is better than 15 dB, and the measured insertion loss is less than 1.2 dB. Moreover, the isolation performance is improved from 2.5 to 15 dB by adding three ports connected with the load resistor. [ABSTRACT FROM AUTHOR]

This article proposes a novel power flow tracing method based on power electronic signaling for peer-to-peer (P2P) electricity trading in dc microgrids. It employs a superimposed low-frequency sinusoidal carrier to trace dc power flows according to the bus port impedance characteristics of power converters. In order to support fair and accurate P2P trading, source-to-load power signaling (S2LPS) and source-to-source power verification (S2SPV) methods are presented. Through S2LPS, the P2P dc power flow from a specific distributed source (DS) to a power load (PL) is determined by detecting the carrier's active power at the PLs bus port. The same carrier is used to check the actual output power of the DS by S2SPV. By implementing S2LPS and S2SPV, the power flows of the system are traced, recorded, and verified by each DS and PL. Accurate power flow tracing is achieved on the physical layer, providing reliable data for P2P electricity trading. The principles of the proposed method are deduced in detail. Furthermore, the modifications to the control loops of DSs and PLs are depicted for implementations in dc microgrids. Finally, a 2.5 kW experimental platform is built to validate the correctness and feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

False data injection attacks (FDIAs) have recently become a major threat to smart grids. Most of the existing FDIA detection methods have focused on modeling the temporal relationship of time-series measurement data but have paid less attention to the spatial relationship between bus/line measurement data and have failed to consider the relationship between subgrids. To address these issues, in this article, we propose a subgrid-oriented microservice framework by integrating a well-designed spatial–temporal neural network for FDIA detection in ac-model power systems. First, a well-designed neural network is developed to model the spatial–temporal relationship of bus/line measurements for subgrids. A microservice-based supervising network is then proposed for integrating the representation features obtained from subgrids for the collaborative detection of FDIAs. To evaluate the proposed framework, three types of FDIA datasets are generated based on a public benchmark power grid. Case studies on the FDIA datasets show that our method outperforms state-of-the-art methods for FDIA detection in these datasets. [ABSTRACT FROM AUTHOR]

The power grid infrastructure is a large-scale, heterogeneous, and complex cyber-physical system, which forms the lifeline of modern societies. The trend of tight coupling of physics, communication, and computation in cyber-physical energy systems (CPESs) is evident by the inclusion of numerous measurement sensors. This contributes to enhancing the monitoring and control functionalities of CPESs. At the same time, the occurrence of adverse effects constitutes a vital dimension of CPES operation. Increasing the resilience of critical energy systems is of key importance for safeguarding the national economy and security. This article considers the problem of optimal estimation with sensing measurements subject to arbitrary corruption resulting from adverse effects. Such signals can cause false situation awareness and/or trigger a sequence of cascading effects leading to an ultimate system failure. We formulate the problem as a constrained optimization with additional prior information posed as a set inclusion constraint on the measurement vector. It is shown that if the prior set satisfies certain conditions, the resulting recovery error bound is improved. The approach demonstrates enhancement of the CPES resiliency by using the Gaussian process as the basis of a prior generative probabilistic regression model using historical data. The validation of the resiliency mechanism using prior information is performed using the New York Independent System Operator grid data, demonstrating 100% successful state recovery for up to 60% of CPES sensor failures. [ABSTRACT FROM AUTHOR]

This brief proposes an effective implementation for addressing permutation ambiguity issue of convolutive blind source separation in frequency domain. Generally, signal envelope and power ratio as common inter-frequency dependence measures are utilized to group bin-wise separated signals for convolutive mixtures, where the new measure of permutation alignment method is represented by the activation matrix of bin-wise spectrum which is based on nonnegative matrix factorization (NMF). Meanwhile, canonical correlation analysis (CCA) rather than the maximum sum of correlation coefficient among different bins, is applied for verifying correlation determinations. In addition, the influence of bin distance and separation quality at each bin are explored to optimize permutation result. Simulation results demonstrate the effectiveness of the proposed technique in real recorded convolutive mixtures. [ABSTRACT FROM AUTHOR]

In this work, a cognitive Raman amplifier controller using an evolutionary optimization strategy for both in-field device calibration and optimal pump power configuration design is presented. The conceived methodology allows to jointly characterize the physical layer properties of the optical fiber span, such as the fiber attenuation profile, the entities of the lumped losses due to mechanical connectors or splices, the polarization coefficients between each Raman pump pair and the Raman efficiency curve. The developed framework expects to work using optical channel monitors (OCMs) as telemetry device and it has been experimentally validated, obtaining outstanding results in terms of precision on a C-band setup. [ABSTRACT FROM AUTHOR]

The standard deviations of the energy and Poynting power densities for an isotropic random field near a perfectly conducting planar boundary are characterized based on quartic plane-wave expansions. For normal and transverse components, different rates of decay exist as a function of electrical distance from the boundary. At large distances, the envelopes for the power are more strongly damped than for the energy, both showing inverse power law decay. The decay for the standard deviation is generally one order faster than that for the corresponding mean. For the normally directed power flux, its standard deviation near the boundary increases linearly with distance. The relative uncertainty of the scalar power is much smaller than that for the Poynting power. Poynting’s theorem for standard deviations is obtained and demonstrates larger standard deviations of the energy imbalance and power flux than their mean values. [ABSTRACT FROM AUTHOR]

Rapid Voltage Changes (RVC) produce sudden illuminance changes that can generate flicker. The IEC 61 000-4-30 standard defines the procedure for the measurement of RVCs, but it does not include a metric to assess the effect of RVCs on the perception of flicker. The IEC 61 000-4-15 standard establishes the specification of a flickermeter, which assesses the effect of voltage fluctuations on flicker by calculating the flicker severity, $P_\text{st}$ , during a 10 min interval. However, $P_\text{st}$ is ineffective to adequately assess voltage variations as fast and short as RVCs. This work analyzes the main characteristics of the RVCs affecting flicker. The relationship between the amplitude and rate of change of the RVC and the instantaneous flicker perception, $P_\text{inst}$ , during the event is quantified. A method to estimate the amplitude of RVCs, and consequently to detect them, is proposed. The method is based on the maximum variation and rising slope of $P_\text{inst}$. The model is tested on 576 hours of recordings from five different low voltage locations. It provides high precision, with a mean deviation below 0.2% in the RVC estimated amplitude. This method could be used by the IEC flickermeter to define a more precise and complete strategy to address the flicker assessment. [ABSTRACT FROM AUTHOR]

We developed a new strength measure, the hybrid multi-infeed effective short-circuit ratio (HMESCR), for evaluating hybrid multi-infeed high-voltage direct current (MIDC) systems. The HMESCR defines the strength of hybrid MIDC systems with line-commutated converter (LCC) high-voltage direct current (HVDC) and voltage-source converter (VSC) HVDC systems. Unlike previous measures, the HMESCR considers the capacity of VSC HVDC systems to provide reactive power and thus, enhance the strength of AC systems connected at different buses with LCC HVDC systems. To demonstrate how the HMESCR reflects power stability (PS) and temporary overvoltage (TOV), we used MATLAB/Simulink software to perform quasi-steady-state analyses and dynamic simulations. The HMESCR can be used to determine the strength of hybrid MIDC systems. [ABSTRACT FROM AUTHOR]

With the increasing development of renewable energy and high-voltage direct current (HVDC) transmission technology, the integration of power electronics-interfaced components has caused sub-/super-synchronous inter-harmonics into power signals, yielding the subsynchronous oscillations (SSOs). Online monitoring and identification of SSOs are crucial to the secure and stable operation of power systems. This paper proposes a data driven SSOs identification method using realistic phasor measurement unit (PMU) data. Three features are extracted via the analysis of a large number of historical PMU data, which can reflect the SSO features and the interference level. An SSOs identification method is proposed through a multiple-support vector machine (SVM) model. It allows us to adaptively select the proper classifier among the multiple-SVM models according to the interference level estimated by the extracted features. This significantly improves the identification accuracy under both low and high interference inputs of a practical power grid. An automatic update function based on incremental learning is also developed to enhance the model performance when the SSO data are subject to new features. Experimental results using field-measured PMU data validate the advantages of the proposed method over other alternatives. [ABSTRACT FROM AUTHOR]

Noise modeling in power line communications has recently drawn the attention of researchers. However, when characterizing the noise process in narrowband communications, previous works have only focused on small-scale phenomena involving fine-grained details. Nevertheless, the communication link's reliability is also affected by long-term noise phenomena that might affect transfer rates at higher layers as well. This paper addresses the problem of long-term noise characterization for narrowband power line communications and provides a statistical analysis of the long-term trends affecting the noise levels. We present a statistical description of the noise process in the time and frequency domains based on real field measurements in the FCC band (10 kHz–490 kHz). The collected data comprises more than 1.8 billion samples taken from three different locations over a time period of approximately ten days. The noise samples have been statistically analyzed by considering stationarity, autocorrelation, and independence. Although our results—being unprecedented—are interesting per se, they improve the noise pattern knowledge, thus paving the way for the design and implementation of more robust PLC protocols. [ABSTRACT FROM AUTHOR]

The status of switches in distribution systems might be changed for protection purposes or to achieve the operation objectives. However, the system topology should be known for the efficacious management and control of these systems. In most practical systems, due to the lack of enough measurements, the topology cannot be identified accurately and speedily. The forecast output can be transformed into the joint probability density function (pdf) of uncertain parameters, e.g., power demands. The measured data and this pdf are first conflated to update the joint pdf to best comply with the measurements. The topology identification problem, i.e., finding the probability of each topology given a set of measured values, is converted to a simpler form, i.e., finding the probability of observing these measured values in this topology. These probabilities are then calculated by tracing how the measurements affect the shape of the new consolidated pdf in each topology compared to the original pdf. The proposed technique employs as much data as available, is able to find the accurate probabilities, and is yet quite fast. The mathematical treatment of extracting such probabilities is presented and the proposed technique is validated in numerical studies in terms of accuracy, speed, and versatility. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) is emerging as the preeminent way to charge electric vehicles, but there appears to be no fair way to measure the power transfer. In this article, Faraday coil transfer-power measurement (FC-TPM) is presented. FC-TPM employs non-contact, open-circuited sense coils to measure the electromagnetic field from WPT and calculates the real power propagating through the air gap between the transmitter and receiver coils. What is measured is the real electromagnetic power, representing the pure dispensation of energy that unambiguously demarcates the losses on either side. FC-TPM was demonstrated to be 0.1% accurate in hardware over an Rx coil misalignment of up to 10 cm using a 1-kW WPT system. Fair metering incentivizes businesses and individuals to make choices that conserve energy and advance technology by providing more information and by properly assigning the financial loss. This article is accompanied by a video highlighting the essential contributions of this article. [ABSTRACT FROM AUTHOR]

Motivated by the dramatic increase of renewable energy and electric vehicle, a variety of customized power modules are rapidly designed and developed. However, it is necessary to expend a long time to examine the new power modules to ensure the reliability concerns via massive experiments, such as power cycling. The deformation characterization of the bare die has a grave impact on the failure of the power module. Therefore, to observe the weak point and presume the cycling lifetime of the power module package, the online characterization of deformation under the field application is significant. Besides, the outcomes can provide confident evidence for the finite element simulation model to conduct research on electrothermal-mechanical stress. In this letter, the mathematical model is created to understand the mechanical deformation induced by electrothermal coupling. To characterize the deformation of the power module in real-time for field application, a noninvasive confocal methodology is proposed. In addition, to confirm the feasibility of the proposed routine, an experimental setup is set up by using the front-to-front converter. The experiment results show that the maximal overall deformation occurs on the middle surface of the die while the edge of the bare die suffers minimal deformation, which corresponds to the simulation results. Besides, the overall and partial deformation errors between experimental and simulation results are within 5% and 7%, respectively. [ABSTRACT FROM AUTHOR]

Wearable health monitoring systems for ubiquitous and continuous evaluation of physiological status are facilitating a paradigm shift in the way healthcare will be delivered in the coming years. As the aging demographic in many developed countries increases, rising healthcare costs and strained hospital resources will result. Furthermore, as the pace of aging in the world is faster than in the past, according to the World Health Organization all countries will face challenges while providing health care to its citizens [1]. Home-based monitoring using low-cost wearable technologies that are capable of automatic diagnosis and supervising the physiological status of subjects may alleviate the excessive demand on the healthcare system. These systems require the development of novel sensor and measurement strategies to automate monitoring of the physiological parameters of interest. Such sensors and measurement systems must be lightweight and have low power consumption, as subjects would have to wear them continuously for long periods of time. Our research group has been developing wearable ultrasonic sensor (WUS) technology for monitoring the dynamical properties of soft tissues [2] in several areas of application. [ABSTRACT FROM AUTHOR]

The use of unmanned aerial vehicles (UAVs) for high-frequency (HF) measurements is a cutting-edge technology that has recently attracted attention. The measurements of far and near fields of antennas, mobile network tests, direction finding, and locating the sources of interference as well as radio-frequency (RF) imaging are a few of the HF applications of UAVs. In this article, we discuss the advantages and capabilities of UAVs for HF measurements as well as some recent progress in the use of UAVs for related types of applications. [ABSTRACT FROM AUTHOR]

We demonstrate that, in an actual network, maximizing the transmission spectral efficiency requires not only to take into account transceiver impairments, but also to consider WSS filtering and flex-grid specifications. In a WDM transmission experiment over a 10-span link covering $\sim 38$ nm, we study achievable rate, bitrate and spectral efficiency for different symbol rates of 62.5, 75, 87.5, 100 and 112.5Gbaud with corresponding channel spacings of 75, 87.5, 100, 112.5, 125GHz, therefore accounting for few GHz bandguard required for potential WSS filtering effect, as well as being compatible with flex-grid configuration. While maximum achievable information rate per transceiver (wavelength) is achieved for the lowest symbol rate, and operating at larger symbol rate maximizes the bitrate per wavelength, to maximize overall fiber spectral efficiency (and therefore, capacity), operation at intermediate symbol rates, from 75 to 100Gbaud in our study, is required as a trade-off between the penalties from transceiver impairments and WSS filtering. [ABSTRACT FROM AUTHOR]

In this letter, we propose and experimentally demonstrate a novel measurement method of mode dependent loss (MDL) in few-mode fiber (FMF) based on mode multiplexing power control. The fiber MDL, between mode groups, is computed from output power of FMF under test by controlling the power of each spatial mode of the photonic lantern. With this method, the MDL between LP01 and LP11 modes in about 9.8km 3-mode fiber is successfully measured. The experimental results obtained with our proposed method agree well with those measured by the FMF optical time domain reflectometer (FMF-OTDR) and the conventional cutback method. And it is also demonstrated that the proposed scheme can be scalable to measure long-distance FMFs with a large number of modes, and be independent of photonic lantern mode crosstalk. [ABSTRACT FROM AUTHOR]

This letter presents an ultralow noise $K$ -band low-noise amplifier (LNA) using substrate integrated suspended line (SISL) technology. A simplified, purely distributed parameter matching network is utilized for simultaneous noise and impedance matching. Different from standard chip-level circuits, a $K$ -band LNA based on board-level platform with low-cost FR4 is proposed. Using the high- $Q$ value of the SISL platform, this LNA shows the advantages of high-power gain, ultralow noise, and self-packaging. According to the measurement, the proposed LNA achieves a 27.7-dB small signal gain with 2.4-GHz 3-dB bandwidth (25–27.4 GHz) and noise figure (NF) of 1.0 dB with 20-mW power dissipation. [ABSTRACT FROM AUTHOR]

This letter presents an enhanced gain broadband power amplifier (PA) design approach that is based on using an integrated diplexer with a phase compensation network to combine PAs of narrower bandwidths (BWs) over a wider overall bandwidth PA. The input and output matching networks of each amplifier are individually synthesized using a wideband matching network. The diplexer is designed using a lowpass/highpass topology approach. The separate amplifiers are integrated with the proposed diplexer, resulting in extended bandwidth and enhanced gain. For verification purposes, a broadband PA is designed and implemented over the frequency range of 2–4 GHz. Measurements demonstrate that the output power varies between 40.1 and 41.2 dBm with a drain efficiency (DE) of 61%–75%. The proposed design achieves a high small-signal gain of 12.5–15.3 dB. The reported saturated power gain is 10.1–11.2 dB. [ABSTRACT FROM AUTHOR]

As a member of the MXene family, tungsten carbide (WC), with its unique physical structure and excellent optical properties, possesses enormous development potentials in ultrafast optoelectronics. In this letter, A WC film saturable absorber (SA) is successfully demonstrated to induce passive Q-switching in an erbium-doped fiber laser (EDFL). The WC nanoparticles (NPs) are synthesized by a hydrothermal method. Stable Q-switched pulses are generated at 1558 nm with a threshold pump power of 141 mW, after inserting the prepared WC film into the EDFL ring cavity. As the pump power ranges from 141 mW to 193 mW, the repetition rate increases from 32.34 kHz to 35.8 kHz, while the pulse duration decreases from $5.5~\mu \text{s}$ to $4.16~\mu \text{s}$. When the pump power reaches a maximum power of 193 mW, the corresponding maximum pulse energy and output power are 81 nJ and 2.9 mW, respectively. To our best knowledge, this is the first report of utilizing WC as SA to achieve Q-switched pulses. Our research results provide a new reference for the realization of pulsed laser using MXene materials and reveal that WC has immense applications in nonlinear optics and ultrafast laser technology, which greatly broadens the frontier of materials for optoelectronic techniques. [ABSTRACT FROM AUTHOR]

Blockage by the human hand/body is an important impairment in realizing practical millimeter-wave wireless systems. Prior works on blockage modeling are either based on theoretical studies of double knife-edge diffraction or its modifications, high-frequency simulations of electromagnetic effects, or measurements with experimental millimeter-wave prototypes. While such studies are useful, they do not capture the form-factor constraints of user equipments (UEs), such as moderate array sizes, gains, and beamwidths. In this work, we study the impact of hand/body blockage with a UE at 28 GHz built on commercial millimeter-wave components. We report five controlled studies with different types of hand holdings/grips, antenna types, and directional/narrow beams. For both hard and loose hand grips, we report considerably lower blockage loss estimates than prior works. Critical in estimating the loss is the definition of a “region of interest” (RoI) around the UE where the impact of the hand/body is seen. Toward this goal, we define an RoI that includes the spatial area where significant energy is seen in either the no blockage or blockage modes. Our studies show that significant spatial area coverage improvement can be seen with a loose hand grip due to hand reflections. [ABSTRACT FROM AUTHOR]

Linear power flow models are widely used in power system analysis. To control the maximum influence of linearization error on decision making, it is important to evaluate the worst-case linearization error (i.e., the error bound). This letter theoretically derives the error bound of linear power flow models based on the truncation error analysis of Taylor series expansion. A cold-start approach is proposed to restrain the error bound. Case studies show that 1) the proposed error bound is tight and effective and 2) the maximum linearization error can be successfully reduced using the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents a new data-driven methodology for power system coherency identification of generator and non-generator buses. This methodology is exclusively based on intrinsic statistical properties extracted directly from observations, without any prior assumption of the probability distribution function (PDF) for the data. The main advances of this proposal are: (i) gathering of statistical information from the data itself despite scenarios where the PDF may change (different inverter-based load and generation scenarios, load levels of the system, and changes in topology); and (ii) assignment of buses into coherent areas without any tuning of parameters, nor manually labeling of huge amounts of training data. This new method, called typicality-based data analysis (TDA), is applied to the correlation metric of the distance between dynamic responses of buses, either voltage angles or frequencies. Simulated signals from a benchmark power system with cases considering the presence of non-synchronous generation and islanding conditions, and real data associated with generation trips in the U.S. Eastern Interconnection are used to corroborate the methodology effectiveness. [ABSTRACT FROM AUTHOR]

This article presents a detection technique for data manipulation attacks in distribution systems using transient information present in the measurements. This technique is based on the fact that any legitimate changes in the system will have a transient response which can be measured by the monitoring system. An algorithm is developed for obtaining the transient solution for three-phase distribution networks. A backward–forward sweep technique is developed for the proposed radial electromagnetic transient program (EMTP) which exploits the radial structure of distribution network. An inclusive transient model compatible with the proposed three-phase radial EMTP for three-phase synchronous generators is also developed. The proposed radial EMTP has been benchmarked with conventional EMTP with 5-bus and 22-bus radial distribution systems and with the same test systems, the proposed detection functionality is evaluated. It is shown that the transient solution provided by radial EMTP are in agreement with the results of conventional EMTP. It is also demonstrated that the deviations between the measured values and the solution of the radial EMTP increase significantly during the transient period when a data manipulation attack is carried out. [ABSTRACT FROM AUTHOR]

This article aims to discuss challenges and performances of a passive load-pull test bench dedicated to the G-band frequencies. The first task of this work is the development of the setup to perform high power generation, impedance generation, and high-power dynamic of measurement. The solution proposed is the association of an external power system of source and detectors, with an integrated synthesizer of impedance. The proposed system requires several analysis steps in order to be validated. On the other hand, special care is dedicated to the calibration of the scalar measurement in the millimeter-wave frequency range. Then, due to the unknown phase at the input and output of the device under test (DUT), scalar measurement can lead to high inaccuracy. Hence, an adaptive calibration is proposed and applied to the measurement of a bipolar transistor at 185 GHz. We highlight the effect of the missing phase information on the accuracy of measurement. Results of the measurement are discussed. [ABSTRACT FROM AUTHOR]

In this article, a two-stage control scheme consisting of an adaptive-gain second-order sliding mode (SOSM) controller and a switched high-gain observer (HGO) is proposed for the three-level neutral-point-clamped (NPC) converter. The adaptive-gain SOSM control method is applied both in the voltage regulation loop and instantaneous power tracking loop, thus, the boundary of the disturbance derivative does not need to be known a priori. Compared with the fixed-gain SOSM, it provides a faster dynamic and a better steady-state response for the NPC converter. On the other hand, the conventional disturbance compensation observer used in the power system suffers from the adverse effects of measurement noise, which limits the performance of the observer. A switched HGO is combined with the adaptive-gain SOSM controller in the voltage regulation loop to address this issue. By using a switched observer gain, the switched HGO greatly diminishes the performance degradation induced by the inevitable measurement noise. Finally, several experiments between the representative extended state observer-based SOSM control scheme and the proposed control method are carried out for a comparison. The results demonstrate the feasibility and effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

The preparations for Exascale computing started over a decade ago and EPCC, the supercomputing center at The University of Edinburgh, was at the heart of these efforts from the beginning. In this article, we revisit some of the key research projects that have paved our Exascale path for the past ten years and look to the future. [ABSTRACT FROM AUTHOR]

False data injection attacks (FDIA) are a main category of cyber-attacks threatening the security of power systems. Contrary to the detection of these attacks, less attention has been paid to identifying the attacked units of the grid. To this end, this work jointly studies detecting and localizing the stealth FDIA in power grids. Exploiting the inherent graph topology of power systems as well as the spatial correlations of measurement data, this paper proposes an approach based on the graph neural network (GNN) to identify the presence and location of the FDIA. The proposed approach leverages the auto-regressive moving average (ARMA) type graph filters (GFs) which can better adapt to sharp changes in the spectral domain due to their rational type filter composition compared to the polynomial type GFs such as Chebyshev. To the best of our knowledge, this is the first work based on GNN that automatically detects and localizes FDIA in power systems. Extensive simulations and visualizations show that the proposed approach outperforms the available methods in both detection and localization of FDIA for different IEEE test systems. Thus, the targeted areas can be identified and preventive actions can be taken before the attack impacts the grid. [ABSTRACT FROM AUTHOR]

With the increased penetration of intermittent distributed energy resources (DERs) and the inclusion of complex loads, the states of an active distribution network (ADN) can experience sudden variations. Most distribution networks are only partially observable using available measuring devices. A distribution system state estimator (DSSE) uses pseudo, i.e., forecasted power injection measurements for the unobserved buses to perform state estimation. The pseudo measurements may fail to capture the sudden change in DERs and loads’ power. Consequently, the conventional DSSEs may fail to estimate the states when there is a sudden change in the loads and DERs connected to the unobserved buses. This paper proposes a forecasting-aided state estimator for ADNs, which can capture the sudden changes in states caused due to intermittent variations in DERs and loads’ power. The estimator requires measurements from a limited number of $\mu $ PMUs, which are placed according to the depth-of-one unobservability criterion. The present work proposes to split the state vector into two parts. The first part captures the gradual Spatio-temporal variations in the states. The second part captures temporally uncorrelated variations in the states that may occur due to the sudden change in power injections. The proposed estimator tracks both state vector components using an l1-regularization-based estimation model. The algorithm is tested on an unbalanced IEEE benchmark test feeder using real load profiles. [ABSTRACT FROM AUTHOR]

As a side-effect-free method, meter coding can successfully detect stealthy false data injection (FDI) attacks without significantly affecting physical plants by encoding the sensor outputs with an invertible matrix. However, since the relationship between the detection of stealthy FDI attacks and the cost of meter coding was not clearly analyzed in existing works, the optimal design of coding schemes has not been well studied. This paper investigates the optimal design of coding schemes based on the analysis of detection conditions for stealthy FDI attacks in power system state estimation. Specifically, detection conditions for stealthy FDI attacks are derived in both general and special coding schemes, which reveal the requirements on the encoded measurements, the coding scheme and the meters in power systems. Utilizing the constraints determined by the detection conditions, the optimization of the special coding scheme is formulated and equivalently simplified, which decouples the design of coding matrix with the other decision variables. Finally, simulation results are carried out on the alternating current (AC) state estimation in the IEEE 14-bus and 57-bus test systems to validate theoretical results on the conditions and cost of detecting stealthy FDI attacks in meter coding. [ABSTRACT FROM AUTHOR]

Basements are increasingly being used as living and working spaces, and the interest in the feasibility of using wireless devices in these environments is increasing. Therefore, it is very important to develop a propagation prediction model for basements. Especially, the isolated communication cell against the satellite or the other building will be promising due to the lack of available frequency resources. However, the propagation model for outdoor-to-basement has not been reported. Only the outdoor-to-indoor in the overground environment has been studied. Therefore, as far as our knowledge, this letter could be the first approach for the building entry loss (BEL) to analyze propagation paths to a basement from outside the building. Experiments were conducted on the basis of three different scenarios for the propagation paths between the exterior of the building and the basement. The BEL was measured at 61 and 71 dB at frequencies of 1.5 and 3 GHz, respectively; these values exceeded the value of about 30 dB of the over-the-ground model described in the International Telecommunications Union Radio-communication Sector P.2109. Further, BEL on the ground floor of the building and the penetration loss between the different floors were measured. Finally, BEL on the building side with parking lot entrance was evaluated. [ABSTRACT FROM AUTHOR]

Mobile networks’ evolution is strictly related to connected cars evolution, making in-car propagation modeling and analysis key enablers in the forthcoming telecommunication competition scenario. The recent availability of mobile device power measurements enriched by GPS position, the so-called 3GPP minimization of drive test (MDT) feature, nowadays, empowers new approaches to propagation studies targeting mobile service and quality improvements. The novelty of the research presented in this article is the use of a huge quantity of MDT geolocated radio measurements in a connected state (more than 370 million during the three-day MDT campaign) along 187 km of Italian A22 Motorway, part of the planned Munich-Bologna EU cross-border corridors for connected and automated mobility (CAM). In particular, MDT measurements of LTE received signal received power (RSRP) are compared between rain and dry road situations, showing how wet environments reshape electromagnetic propagation, even for LTE frequency bands (below 3 GHz) that have line-of-sight propagation marginally influenced by rain. Explanations of measured effects and simulations are presented. The rain effect on cellular propagation should be carefully considered in the perspective of connected car evolution, specifically considering new worldwide available 5G bands, more affected by rain situations, and autonomous driving scenarios. [ABSTRACT FROM AUTHOR]

At present, superconducting power technology has been applied more and more in the ac field, such as ac superconducting current limiter, ac superconducting cable, and so on. Critical current is the key parameter in the design, manufacture, and operation process of superconducting devices, but few studies were carried out on the ac critical current of superconductors now. In this article, a method for measuring the ac critic al current of the HTS coil based on the thermal stability was proposed, the ac critical current measurement experiment of the superconducting coil is carried out, and the electromagnetic–thermal coupling model is built to analyze the quench principle of the superconducting coil. This article explains the principle of ac critical current from the balance of heating and cooling and gives the rule that the value of ac critical current changes with frequency. [ABSTRACT FROM AUTHOR]

This article demonstrates the protection effects using transient voltage suppressor (TVS) diodes based circuits under high-power microwave (HPM) pulses. Two types of TVS diodes were studied, and their dynamic resistances versus the input power were obtained. Five types of topologies using these two TVS diodes based circuits were designed and compared with their voltage–ampere characteristics. The dynamic resistances of each branch of two typical circuits were simulated and compared. These TVS diodes based protection circuits were measured under HPM pulses with their protection effects recorded. The highest protection ratio of these circuits is approximately 17–20 dB when the input power of HPM pulses ranges from 50 to 62.5 dBm. The simulated and measured results show some correlations. This analysis is useful for further electromagnetic protections under HPM pulses. [ABSTRACT FROM AUTHOR]

The beam profile of an antenna can be measured by scanning it over a calibration source in the far field and recording the output power from the antenna as a function of the angle between the direction of the source and antenna axis. For large antennas that do not fit into an anechoic chamber, measurements are often made in a test range where the source is mounted at a large distance and height. However, this method has certain limitations, as constraints on the height of the source make measurements at high altitude angles difficult, and the measurement may also suffer from reflections from the ground. [ABSTRACT FROM AUTHOR]

In this article, a six-port reflectometer is proposed, which utilizes nonmatched power detectors. In the presented solution, the signals reflected from power detectors are efficiently used to obtain a signal flow required for correct measurements. As a consequence, impedance matching networks for power detectors are no longer needed. Simultaneously, due to its balanced topology, the developed six-port exhibits advantageous measurement conditions and theoretically ideal matching at both its input and measurement ports. To experimentally validate the proposed concept, a six-port reflectometer operating at 2.4 GHz is designed, manufactured, and utilized in reflection coefficient measurements. The obtained results are consistent with the values measured using a commercial vector network analyzer. For additional verification, the impact of power detectors’ asymmetry is investigated theoretically and experimentally. [ABSTRACT FROM AUTHOR]

In this article, we investigate the potential enhancements in signal reliability which can be achieved using a millimeter-wave distributed antenna system (DAS) within an indoor environment. To achieve this, we measured the signal power simultaneously received at nine ceiling-mounted access point (AP) locations likely to be used in future indoor DAS deployments while a mobile user imitated making a voice call on a hypothetical user equipment. Key metrics, associated with the performance of multiple antenna systems, such as the cross correlation coefficient (CCC) and channel power imbalance (CPI) are determined. It was found that line-of-sight (LOS) and quasi-LOS (QLOS) links with the APs typically led to higher CCC values than the non-LOS (NLOS) cases. Similarly, LOS and QLOS links typically produced higher CPI values between APs than the NLOS case. To enable the reproduction of our results, we have successfully applied autoregressive moving average and autoregressive integrated moving average modeling to the CCC and CPI time series. The performance improvement that can be achieved using a DAS instead of a single AP was evaluated using three commonly deployed diversity combining schemes, namely, selection combining, equal gain combining, and maximal ratio combining along with three AP selection mechanisms, namely, per-sample random AP selection, one-shot AP selection, and per-sample optimal AP selection. Finally, we have provided some useful insight into the influence of differing AP numbers on the diversity gain when considering the aforementioned AP selection methods. [ABSTRACT FROM AUTHOR]

Dynamic state estimation (DSE) accurately tracks the dynamics of a power system and provides the evolution of the system state in real-time. This paper focuses on the control and protection applications of DSE, comprehensively presenting different facets of control and protection challenges arising in modern power systems. It is demonstrated how these challenges are effectively addressed with DSE-enabled solutions. As precursors to these solutions, reformulation of DSE considering both synchrophasor and sampled value measurements and comprehensive comparisons of DSE and observers have been presented. The usefulness and necessity of DSE based solutions in ensuring system stability, reliable protection and security, and resilience by revamping of control and protection methods are shown through examples, practical applications, and suggestions for further development. [ABSTRACT FROM AUTHOR]

Customer-level rooftop photovoltaic (PV) has been widely integrated into distribution systems. In most cases, PVs are installed behind-the-meter (BTM), and only the net demand is recorded. Therefore, the native demand and PV generation are unknown to utilities. Separating native demand and solar generation from net demand is critical for improving grid-edge observability. In this paper, a novel approach is proposed for disaggregating customer-level BTM PV generation using low-resolution but widely available hourly smart meter data. The proposed approach exploits the strong correlation between monthly nocturnal and diurnal native demands and the high similarity among PV generation profiles. First, a joint probability density function (PDF) of monthly nocturnal and diurnal native demands is constructed for customers without PVs, using Gaussian mixture modeling (GMM). Deviation from the constructed PDF is utilized to probabilistically assess the monthly solar generation of customers with PVs. Then, to identify hourly BTM solar generation for these customers, their estimated monthly solar generation is decomposed into an hourly timescale; to do this, we have proposed a maximum likelihood estimation (MLE)-based technique that utilizes hourly typical solar exemplars. Leveraging the strong monthly native demand correlation and high PV generation similarity enhances our approach's robustness against the volatility of customers’ hourly load and enables highly-accurate disaggregation. The proposed approach has been verified using real native demand and PV generation data. [ABSTRACT FROM AUTHOR]

Modal decomposition of measurement equations has already been shown to simplify the formulation and resulting computational complexity of three-phase state estimation of systems where all the transmission lines are three-phase and fully transposed. When there are non-transposed and/or mixed-phase lines, modal decomposition can no longer fully decouple the three-phase measurement equations. This paper addresses the above shortcoming by proposing a simple yet practical solution based on the commonly used numerical compensation techniques. Thus, it enables application of the powerful decoupling approach to any type of three-phase networks which may contain non-transposed or mixed-phase lines and are fully observable by PMUs. The proposed procedure modifies the measurement set by deriving additive terms that compensate for the neglected unsymmetrical effects. It will be shown that unbalanced systems including non-transposed and mixed-phase elements, can still be transformed into three decoupled subsystems and solved in parallel by the proposed approach. Performance of the proposed algorithm is validated against several IEEE test cases. [ABSTRACT FROM AUTHOR]

Consider the problem of mitigating the impact on data integrity of phasor measurement units (PMUs) given a GPS spoofing attack. We present a sparse error correction framework to treat PMU measurements that are potentially corrupted due to a GPS spoofing attack. We exploit the sparse nature of a GPS spoofing attack, which is that only a small fraction of PMUs are affected by the attack. We first present attack identifiability conditions (in terms of network topology, PMU locations, and the number of spoofed PMUs) under which data manipulation by the spoofing attack is identifiable. The identifiability conditions have important implications on how the locations of PMUs affect their resilience to GPS spoofing attacks. To effectively correct spoofed PMU data, we present a sparse error correction approach wherein computation tasks are decomposed into smaller zones to ensure scalability. We present experimental results obtained from numerical simulations with the IEEE RTS-96 and IEEE 300 test networks to demonstrate the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

In this article, we design and experiment a far-field wireless power transfer (WPT) architecture based on a distributed antenna system (DAS), so-called WPT DAS, that dynamically selects transmit antenna and frequency to increase the output dc power. Uniquely, spatial and frequency diversities are jointly exploited in the proposed WPT DAS with low complexity, low cost, and flexible deployment to combat the wireless fading channel. A numerical experiment is designed to show the benefits using antenna and frequency selections in spatially and frequency selective fading channels for single-user and multiuser cases. Accordingly, the proposed WPT DAS for single-user and two-user cases is prototyped. At the transmitter, we adopt antenna selection to exploit the spatial diversity and adopt frequency selection to exploit the frequency diversity. A low-complexity over-the-air limited feedback using an IEEE 802.15.4 RF interface is designed for antenna and frequency selections and reporting from the receiver to the transmitter. The proposed WPT DAS prototype is demonstrated in a real indoor environment. The measurements show that WPT DAS can boost the output dc power by up to 30 dB in a single-user case and boost the sum of the output dc power by up to 21.8 dB in the two-user case and broaden the service coverage area in a low cost, low complexity, and flexible manner. [ABSTRACT FROM AUTHOR]

Current research about battery-less fuel cell-based point-of-care (POC) devices study energy extraction and the measurement separately. In this article, we purpose a self-powered architecture that extracts energy efficiently from a fuel cell and performs a measurement simultaneously. The prototype uses a discrete power management unit based architecture with a power consumption lower than 36  $\mu$ W. We have tested it with ethanol, lactate, and methanol-based fuel cells, being able to perform a fuel concentration measurement while it extracts energy from fuel cells. The solution exhibited a minimum efficiency and maximum start-up time for the ethanol, lactate, and methanol-based fuel cells of 80% and 12 s. The architecture applies to other fuel cells, and the results show how this solution can help us face the current POC's autonomy challenge. [ABSTRACT FROM AUTHOR]

This paper presents a novel method to estimate the power consumption of distinct active components on an electronic carrier board by using thermal imaging. The components and the board can be made of heterogeneous material such as plastic, coated microchips, and metal bonds or wires, where a special coating for high emissivity is not required. The thermal images are recorded when the components on the board are dissipating power. In order to enable reliable estimates, a segmentation of the thermal image must be available that can be obtained by manual labeling, object detection methods, or exploiting layout information. Evaluations show that with low-resolution consumer infrared cameras and dissipated powers larger than 300 mW, mean estimation errors of 10% can be achieved. [ABSTRACT FROM AUTHOR]

Aged cable segments in underground power distribution systems will gradually develop into severe faults. The location of aged cable segment is essential for ensuring system reliability and reducing maintenance cost, but is rarely studied by the existing research. In this article, a novel aged cable segment detection and location method based on wide frequency range transfer function (TF) measurement and deep learning approaches is proposed to fill the gap. The relationship between the measured TF and cable ageing parameters is analyzed, and two models with combined sparse autoencoder and convolutional neural network are trained to estimate the aging location and severity. A transfer learning approach is further developed to improve the model performance for various online situations. Experiments are conducted which prove the effectiveness and generalization ability of the proposed method. Compared with existing approaches, the proposed method shows better performance under different ageing situations, even smooth ageing scenarios. [ABSTRACT FROM AUTHOR]

A novel fast measurement method based on Brillouin gain spectrum (BGS) and Brillouin beat spectrum (BBS) in a complex index profile fiber has been proposed to realize simultaneous measurement of distributed temperature and strain. An interesting phenomenon that the temperature/strain sensitivities of the power on the BGS slope and the power on the BBS peak are very different has been discovered and utilized for temperature and strain sensing. By means of only measuring the power trace of the BGS slope and the power trace of one BBS peak along the sensing fiber, the distributed temperature and strain can be measured by using the Brillouin optical time-domain reflectometry (BOTDR) without scanning the Brillouin spectrum. The temperature and strain measurement uncertainties of the proposed method are one order of magnitude lower than that of the BBS-based measurement method. In a proof-of- concept experiment, the temperature and strain of the 2 km large effective area fiber (LEAF) are measured at a spatial resolution of 3 m within 18 s. [ABSTRACT FROM AUTHOR]

Enhancing the spatio-temporal observability of distributed energy resources (DERs) is crucial for achieving secure and efficient operations in distribution grids. This paper puts forth a joint recovery framework for residential loads by leveraging the complimentary strengths of heterogeneous measurements in real time. The proposed framework integrates low-resolution smart meter data collected at every load node with fast-sampled feeder-level measurements from limited number of distribution phasor measurement units. To address the lack of data, we exploit two key characteristics for the loads and DERs, namely the sparse changes due to infrequent activities of appliances and electric vehicles (EVs) and the locational dependence of solar photovoltaic (PV) generation. Accordingly, meaningful regularization terms are introduced to cast a convex load recovery problem, which will be further simplified to reduce the computational complexity. The load recovery solutions can be utilized to identify the EV charging events at each load node and to infer the total behind-the-meter PV output. Numerical tests using real-world data have demonstrated the effectiveness of the proposed approaches in enhancing the visibility of grid-edge DERs. [ABSTRACT FROM AUTHOR]